I wrote a column last week in which I dismissed the chances of Republican Scott Brown actually winning next Tuesday’s Senate special election in Massachusetts. The race would be close, I figured — 53-47 for Coakley, or something like that — but the state’s blue tint would be just enough to save the Democrats.

I’d now like to qualify that prediction. Coakley’s internal poll last night, I’ve been told, showed her barely ahead, 46 to 44 percent. The momentum clearly favors Brown, and one very smart Massachusetts Democrat I know told me this morning that “this may be too far gone to recover.”

So I was wrong: Brown may actually win.

Two presidents campaigning for Coakley, the ghost of St. Teddy hovering over the election, Democratic groups outspending Republican ones by a two-to-one margin — and it’s a jump ball five days out. Or is it? A Research 2000 poll out today shows Coakley up by eight, which might be the usual R2000 tilt at work but doesn’t sound implausible to me. The fact is, Coakley still has every incentive to scare the hell out of her supporters by claiming the race is closer than it is. Ace says he’s fine with that, that winning a high turnout election in Massachusetts will only make victory sweeter, but … Brown can’t win a high turnout election. He can win an election with average turnout among Democrats if indies and Republicans turn out hugely for him (which they probably will), but with all the big names, money, and earned media the Dems are pouring in there, it’s less and less likely that turnout will be average. At this point, the bigger this election gets — and a video statement from the president calling it big makes it officially Big, I’d say — the harder it is for Brown. Even if that moneybomb isstill exploding.

Here’s his new ad, which Ben Smith calls his first “really negative one.” AP pessimism meter level check: 2.0, down half a point from earlier this week, indicating a likely chance of heartbreakingly narrow defeat.